The object of this paper is to present a study of the problem of development management and cost control in a Defence setting. It does not offer any simple final solution, nor indeed claim some sudden breakthrough. It is, however, felt that progress in this field in the UK has been retarded by the lack of publication of attempts to think about this problem. In these circumstances, the processes of both criticism and cross-fertilisation of ideas, so essential to progress in any field of endeavour, cannot get to work and there is a high probability that the same mistakes will be made over and over again. If the publication of this paper does no more than stimulate others to publish their thoughts on this important problem, a major part of the objective of preparing it will have been achieved.

The work of the Engineering Department of an airline covers four main functions which are interdependent:

1. 1. The maintenance in service of the airline's fleet in a manner which optimises the economy of the airline and prevents reduction in the inherent design levels of safety and reliability.

2. 2. (a) Develops ideas and specifications for future equipment in consultation with other departments in the airline, or

   (b) Analyses the suitability of available or projected equipment offered by manufacturers, again in consultation with other departments.

3. 3. Purchases the equipment finally selected, together with the backing stores necessary for the planned operation, and creates the necessary maintenance facilities (or contracts with someone else to do the work, where this is more efficient).

4. 4. Integrated with (1) is the task of engineering develop ment of the fleet to correct deficiencies found in service or to improve its performance of the required task.

With the introduction of each new generation of combat aircraft it has become popular to assume that they will be operated in a more conservative manner than previously and that less attention, therefore, need be paid to their spinning characteristics. Current experience, however, shows that inadvertent spins will continue to occur, and must be allowed for, if these aircraft are to be operated effectively and to the limit of their capability.

In this connection the Hunter provides an interesting case history, since it has been put to widescale use in a variety of roles and its erect and inverted spinning characteristics have been thoroughly investigated. These characteristics will be described both for their own sake and because of the applicability which they have to current high performance aircraft.

The Plowden Committee has been considering ”… the future place and organisation of the Aircraft Industry in relation to the general economy of the country taking into account the demands of national defence, export prospects, the comparable industries of other countries, and the relationship of the Industry with Government activities in the aviation field.” Against this background of inquiry into the future structure of the Industry, it seems opportune to consider in some detail the actual process of mergers and reorganisation which occurred in the Aircraft Industry during the period 1957-60. This paper will attempt to explain the reasons for the mergers, the development of Government policy towards the Industry during this period, and the actual process of events which produced the recent industrial structure.

The task of completing an inventory of Canada's forests is an immense one and it is not surprising that aircraft have been used in Canadian forest inventories ever since they became available in reasonable numbers. As will be seen, the nature of the forest to be surveyed and the characteristics of the organisations engaged in forest inventories provide the strongest argument in favour of aircraft.

Canadian forest inventories, like all forest inventories, are concerned with estimating the area of forest land and the description of the timber on that area. More specifically, one usually seeks an estimate of timber volume by tree species and size classes and information on various characteristics of tree quality, such as extent of decay and tree form.

The history of the application of fungicides is one which shows a tendency to use ever decreasing quantities of spray liquid to the acre; the reason for this is obviously one of economics. The classification of various spray techniques is discussed with particular reference to the term ultra low volume. This may be defined briefly as the spraying of such extremely small volumes of liquid to the acre that it becomes impossible to use a simple aqueous medium as carrier. The reasons for this are given and the advantages of using special formulating agents noted.

The success of the low volume technique of spraying potatoes for the control of blight is illustrated with a series of blight progress curves, showing that 5 lb of copper oxy-chloride applied at 50 gpa gives identical results to a similar rate of copper at 2 gpa. Copper estimations made on leaf samples from the top, middle and bottom leaves of a potato crop sprayed at 100 gpa and 5 gpa respectively show that the mass distribution of copper is much more uniform in the high volume plots than in the low volume plots. However, the largest quantities of copper are found in the top layers of the plots sprayed at low volume.

It must be obvious to anyone who has anything to do with agricultural aviation, that the training of agricultural pilots has, lately, received more attention than ever before. There are several good reasons for this and before speaking of the training itself, as it is carried out in the different countries, I feel that it might serve a useful purpose to go into these reasons more deeply.

The first part of the subject, that is, the reason why we are forced to pay more attention to the training of agricultural pilots than we have in the past, I have often mentioned both by word of mouth and in writing. This will not prevent me, however, from doing so again. This whole question is, in my opinion, of prime importance.

Pesticides are commonly applied either as aqueous solutions or emulsions, using spray tips designed to break up the liquid into a relatively fine spray. One consequence of this practice is that a variable proportion of the spray, composed of smaller droplets, drifts out of the target area. Some weedkillers, such as the derivatives of 2,4-D, are effective in minute quantities and a small amount of drifting spray can, therefore, cause considerable damage to sensitive crops grown down-wind. If the spray contains an insecticide the same amount of drift will take place under the same conditions. The insecticide is not likely to damage adjoining crops but it may not be wanted, it may cause undesired contamination of pasture land, it may be harmful to domestic animals or to wild life, and it can be said to contribute to the much-discussed problem of environmental contamination. However, it is not the purpose, here, to pursue the controversy about the use and misuse of pesticides. Sufficient to say that drift always results in some wastage of valuable spray liquid, it detracts from the efficiency of spraying operations and it is a problem which everyone would like to overcome.

Ample evidence(1, 2, 3) exists to indicate that, in the presence of contaminated water and microbiological growths, the present widely used nitrile rubber compositions for lining integral fuel tanks of aircraft do not always offer satisfactory protection against corrosion. Failure of the lining sometimes occurs, which leads subsequently to pitting and inter-crystalline corrosion of the underlying aluminium alloy, resulting in structural weakening of the affected members, and in some instances actual perforation of the aircraft skin. In the majority of observed instances, the corrosion occurs beneath a section of the lining which has become deteriorated. This deterioration occurs in areas where water lies in contact with the nitrile rubber lining, especially where micro-biological slimes have developed at the interface of water, fuel and tank lining. Our evidence in kerosine systems indicates that these slimes are essentially fungal in nature, the predominant fungus being Cladosporium resinae (Lindau) de Vries, and that the associated water may range from low levels of electrolyte contamination to about 3500 ppm of salinity. We are not unmindful of the fact that numerous bacterial species have been found in such slimes, and may well contribute to the mechanism of deterioration of the lining, and the subsequent corrosion of the metal.

Vortices shed from cooler tubes can excite standing pressure waves in coolers if the vortex shedding frequency coincides with the standing wave frequency(1, 2, 3, 4). If resonant conditions are encountered in a particular cooler the single vortex shedding frequency may be suppressed by fitting in-clined splitter plates into the coolers. These splitter plates also “detune” the coolers by raising the resonant frequencies.

Splitter plates of this type were used recently to eliminate severe noise and structural vibration in a new cooler for the 3 ft wind tunnel at the Royal Aircraft Establishment, Bedford.

The author mentioned in his Main Lecture(1) the success achieved in the analysis of three-dimensional media, for small and large displacements, as well as anisotropic and non-elastic behaviour, by the introduction of tetrahedron elements of constant strain and stress(2), see also technical note 1 of this series(3). A cardinal point of the theory is the specification of natural strains, stresses and stiffness. At the same time attention was drawn to certain difficulties arising in the interpretation of the stresses at the nodal or other points, which are more severe than for constant strain triangles, the corresponding elements in the two-dimensional case. It was suggested in the lecture that a considerable improvement might be achieved by the specification of a linearly varying strain or stress state within the tetrahedron. The solution of this problem, limited to small displacements, is summarised in this fifth technical note and its application is to be demonstrated on an example in the printed lecture.